Regenerated cellulose apparatus



April 13, 1943.

F, P. ALLES REGENERATED CELLULOSE APPARATUS Filed Dec. 13, 1941fidiZCf-FPAZAEJ INVENTOR I ATTORNEY Patented Apr. l3,

REGENERATED CELLULOSE' APPARATUS Francis P. Alles, Waynesboro, Va.,assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., acorporation of Delaware Application December is, 1941, Serial No.422,803

3 Claims. (01. 34-124) This invention relates to the drying ofcontinuous non-fibrous cellulosic sheet material, espe- 1 cially to theremoval of water from gel regenerated cellulose web in such a way thatthe dry product is substantially completely and uniformly flat; Moreparticularly it appertains to improvements in the design, constructionand operation "of the drier rolls employed in the drying operaoperationwhich fits the product for immediate use or storage. When the web isready for this drying operation it contains 350% to 400% water, so itwill be apparent that a very substantial volume change must, take placeduring the water removal. This change manifests itself in shrinkage(loss of area and thickness) of the web. The properties of the sheetwrapping material are dependent to a large extent upon how thisshrinkage is regulated, and a host of patents relating to the dryingstage, for example, U. S. A. Patents 1,606,824 (Brandenberger),2,046,553 (Edwards), 2,099,160 (Charon), 2,099,162 (Eberlin), 2,115,132(Alies 8: Edwards), and 2,141,377 (Chylinski) l The art has nowdeveloped to a point where drying the web by passing it around heatedrolls is generally believed to be the most desirable scheme availablefor commercial scale operation. This method has had a major draw-back,in that no really satisfactory way of supplying heat to the rolls hasbeen available. Under present day operating speeds it has heretoforebeen impossible to distribut the heat over the drying roll in a patternwhich prevented over-drying of certain portions of the web. "As a resultof the uneven heating, the final sheet material is not uniformly flat,and difficulty is encountered in operating w ppins hinery employing thesame at high speeds. Cutting, slitting, laminating, crimping, and likeoperations must also be carried out at slower speeds than would bepossible if a better material were available.

It was the primary object of this invention to.

prove continuous web. drier operation by special drier rollarrangements. Still further objects were to produce apparatus for dryingcontinuous lengths of non-fibrous cellulosic web in which an evendistribution of heat is provided and im proved uniformity of drying isobtained; to produce non-fibrous sheet material that is substantiallyuniformly flat and straight when'stretched without being placed underexcessive tension: and to provide improved meansfor continuously dryinggel non-fibrous webs. A general advance in the art, and other objectswhich will appear hereinafter, are also contemplated.

It has now been found that distributing steam in the interior of adrying roll in the manner described hereinafter in detail, accomplishesthe aforementioned objects. Added improvement is obtained by arrangingthe drying rolls in a special sequence, also described in detailhereinafter. The present invention provides, inter alia, an improvedsteam distributor to. be positioned axially within the drying roll.

design improved drier rolls; to improve the results How the foregoingobjects and related ends are accomplished will be apparent from thefollowing exposition, in which are disclosed the principle and diversembodiments of the invention, including the best mode contemplated forcarrying out the same. The written description is amplified by theaccompanying drawing, in which:

Figure 1 is a scheme showing a roll drier and adjacent portions of aviscose-regenerated cellulose sheetcasting machine;

Figure 2 is a fragmentary elevation view partly in section of the drierroll and steam distribution unit of this invention;

Figure 3 is a fragmentary perspective view of th heating element of thepresent invention:

Figure 4 is a sectional view along the line 4-4 of Figure 2; and vFigure 5 is a fragmentary elevation view, partly in section,corresponding to Figure 2, of one end of the heating element.

Referringnow to the drawing, there is illustrated at MI in Figure 1 atank containing the softening bath 33 l through which the continuousregenerated cellulose film 3 passes immediately before being transferredto the drier in the well known method of manufacturing regeneratedcellulose sheet-wrapping material. The numerals MI and I indicate rollswhich simultaneously.

2 numbers I through '21, after which the dried drier roll.

product passes to a winding mechanism comprising a driven (with frictionclutch'and overdrive) core for the mill roll l6 supported on a bracketH, which is secured to an upright l8.

"As shown in Figure 2, the "individual rolls 32'! comprise an outershell 325-supported on a tubular shaft 313 by means of a disc-like endclosure piece 326. A pulley 3121s also mounted on the shaft 310 adjacentthe aforementioned endof the A light friction means (not shown) connectsthe roll with the pulley in the actual machine. This permits someslippage in case the driving force exerted by the pulley should begreater than that desired. The pulley and the the disc 326 isimperforate so that the. heating steam and water condensed therefromwill not escape in the vicinity of the driving pulley. The correspondingpiece 328 at the opposite end of the roll has openings 329 (or it may bereplaced by a spider arrangement) to prevent the accumulation of waterin the roll. a The shaft 310 rests on end supports (not shown). The endof this shaft, through which the heating steam or other liquid isadmitted; is closed with a sleeve 4| and cooperating cap 42.

Pipe 2| carries the steam through the cap into the interior of the rollshaft. This pi-pe extends a considerable distance into the shaft, and isan important part of the steam distribution arrangement As shown inFigure 2, thepipe is supported on one side of the roll by disc-likemember 32, and atits end on the opposite side of the roll by a member22, which also serves as a gastight closure for the end. Surroundingpipe 2| is a cylinder 3| closely fitting inside the shaft, and

'closed at one end by the disc 34. The closed space within this tube isdefined by the member 34 and the previously mentioned member 32.

The steam entering through the pipe 2| (Figure.

with the slot 3'" in the shaft 310 into the interior of the drying roll.

In Figure 5, a shaft and steam distribution arrangement similar to thatof Figure 3, is shown,

but in this case an aperture 23a is used in .the

ventionalmanner, and as a final step in the wet treatment, passedthrough an aqueous bath of 5%. glycerol.

At this stage were 12 inches in outside diameter and 76 inches long, andwere supported on trunnions, one of which was hollow to permit access tothe interior of the roll. The shafts 310 upon which the rolls anddriving pulleys rotated, were iron tubes 3 inches in diameter. The slot3' extended for 52 inches, and was centered on the center line of theroll. The shafts were lined with brass tubes 3|, and

= taining it in position at the center of the drying roll.

The orifices 23 and 2311 were spaced 27% inches from the center line ofthe roll. The

perforations in the tube 3| were spacedat 2 inch intervals opposite theslot 3' in the shaft.

The steam delivery pipes 2| entered all rolls on the same side, but aspreviously pointed out, the steam was delivered to the distribution tubeand lower rolls. As a further refinement, all

, the tubes 3| in which steam entered from the place of the previouslydescribed aperture .23 for the purpose of admitting the steam to thetube 3|- at the opposite end. In the drier these two types of steamdistributors alternate. This is indicated by the indicia on the rolls inFigure 1. As there shown, the steam is admitted at the right end of thetube 3| in roll I, at the right end of tube 3| in roll 2, at the leftendv of tube 3| in roll 3, at the left end of tube 3| in roll 4, at theright end of tube 3| in roll 5, etc. In this way,any unevendistributionofl the heatin the rolls is alternated back and forth acrossthe web 3| as it passes through the drier. The arrangement justdescribed has the additional advantage that the surfaces of the webalternate in contacting pairs of rolls having opposed steam inletarrangements. In one specific embodiment of the invention, a viscosesolution comprising 8.5% cellulose and 5.5% sodium hydroxide, wasextruded into a coby desulfuring, bleaching and washing in the contube2| on the left side (3L, etc.) of the machine, as illustrated in thedrawing, had a hole in the tube 3| centered on the center .line of theroll, and all the tubes 3| in which steam entered on the right side hadthe series of perforations displaced one inch from the center line."

distances of 38 inches and 40 inches, respectively. In this manner thearea's of-the regenerated cellulose web treated by the heat from the twosets of perforations were staggered, so that the effective distancebetween areas of maximum heatingwere one inch, a distance so smallthatno band streaks on the film were apparent.

The steam entering the distributor tubes was controlled inflow,.temperature and pressure by conventional apparatus, thecharacteristics and adjustments of which are well knownin the art. v

Aluminum and its alloys are the preferred materials of construction forthe drier rolls because of their light weight, high heat conductivity,etc. Other .metals such 'asiron and its alloys, for example, stainlesssteel, copper, brass, etc., may be employed somewhat less satisfactorilyfor the construction of the roll itself. The steam distributor tubes 3|on the interior of the roll shaftmay be made of any suitablenon-corroding metals and alloys, such as stainless steel, brass,aluminum, etc, Special devices such as those already knownin the art maybe employed to remove the water of condensathe web contained 350%waterand 15% glycerol, based on the'cellulose, and was The perforationsin the tubes 3| extended over and satisfactorily operative arrangementfor draining off the water. In some cases it has been found desirable tooperate the rolls with about one inch of water in the bottom, in orderto further equalize the heat distribution. An inwardly projecting beador collar of comparable terial beingprocessed and the use to whichit isto be put.

Steamis very convenient for. heating the drying rolls, but'other heatingfluids may be employed if desired. In ordinary operation the heatingfluid temperature is regulated sothat the roll surface is kept withinthe temperature range 90-l00 C., but other temperatures may beemdimensions at the open end of the roll accomplishes this purposesatisfactorily. Where the rolls are operated relatively free of water,the steam may be directed in a downward direction so as to play upon thelowest part of the roll. Where considerable water is desired at thebottom of theroll, the steam projected upwardly.

or in any desired direction. The diameter of the orifices 33 in thedistributor 23!, and their general arrangement, are. to some extentdetermined by the drying pattern desired for the type of film'beingmanufactured by the particular conditions of operation encountered. Afull discussion of drying patterns will be found in the Charch & Allesapplication mentioned above, and there is no need to burden thisspecification with such details at this time. Suflice it to say thatadjustment and regulation of the steam controllin apparatus, to securethe desired variations, is with n the skill of those versed in the arthaving familiarity with the foregoing disclosure.

The dimensions given in the specific example are not necessarilycritical. Rolls from 50 inches to 120 inches long and from 10 to 15inches.

indiameter are often encountered in the art, and proportionatevariations in the dimensions of the steam distributing apparatus may bemade to produce aim-action satisfactory for pressure may be employedwith suitable modifications of the controls, orifices, etc. i

. Where the ends of the roll are opened, it is preferable to operateunder such conditions that the steam will be reduced to water ratherthan in escape in large quantities into the surrounding 7 atmosphere.

Gel materials other than regenerated cellulose web, for example, lowsubstituted methyl cellulose and the 1lke..may be successfully dried onthe previously described' apparatus. Webs of different thicknesses maybe dried with suitable adjustment of the conditions, and the number ofdrying rolls employed will depend upon the. material being produced andvarious operating conditions encountered. i

It is not intended by the preceding tolimit the invention to the dryingof cellulosic film.

since it is as applicable to gelatin, caseinand' the like as it is tocelluloseethers, for example, glycol cellulose, and cellulose esters,for example, cellulose acetate. I

Similarly, it is not intended to limit the invention to, the employmentof glycerol as a soft ener. Other softeners and combinations ofsofteners may be employed, depending upon the ma Thisfactor should beobserved in designing sult desired.

ployed, depending upon the results desired.

It will be appreciated that any specific pattern or arrangement of theright and left heating fluid feeds may be employed, depending upon there- The arrangement illustrated in Figure 1, wherein the steam isadmitted to the central distributor tubes in rolls l and 2 from theright side, in 3 and 4 from the left side, etc.,

has been found to give the fiattest sheet, and since a fiat sheet is thepresent desideratum, it was most convenient to illustrate thecorresponding drier roll arrangement.

Most of the advantages of the present invention are believed to beobvious. The drier apparatus provides a more uniform distribution ofheat, and provides a process of compensation of factors influencing thedistribution of heat with out necessitating complicated apparatus.

Regenerated cellulose film dried according to the preferred embodimentsof this invention is substantially completely and-uniformly flat, and ofsubstantially uniform moisture 7 content throughout. Because of itsuniform flatness, the film so produced can be run through subsequentprocessing operations such as coating, slitting, laminating, crimping,etc., at less cost and greater production rates. The product isespecially well suited for use in modern high speed wrapping machinery,and ensures rapid operation and perfect packaging.

Because of the efficient and uniform applica tion of the heating mediumin the present meth-- The fact that the elements 2|, 3i, 4| and 42- forma unit which may be bodily removed from the shaft 310, is an importantadvantage in the I construction and maintenance of the apparatus;

.As many apparently widely different embodiments of this invention maybe made without departing from the spirit and scope thereof, it is to beunderstood that this invention is not limited to the specificembodiments thereof except as defined in the appended claims.

I claim:

1. A steam distributor for a web drying roll compising three concentrictubes, the innermost tube being connected to a source of heating fluidat one end and closed at the other end, the intermediatetube beinglarger than the innermost tube whereby a compartment therebetween isformed, the said' compartment being closed at both ends, an openingthrough thewall of the innermost tube to provide communicationbeopenings in the wall of the intermediate tube.

and a slot in the outer tube registering with the said line "ofdischarge openings to permit direct access of the heatingfluid from theaforementioned compartment to the chamberbetween the exterior of theouter tube' and the inside of drying roll.

. 2. A drier roll for regenerated cellulose web including 9, hollow'cyiindrical aluminum shell tributor shaft upon which said shell ismounted for tree rotation, said shaft comprising three concentric tubes,the innermost tube being connected to a source of heating fluid at oneend and closed at the other end, the intermediate tube being larger thanthe innermost tube whereby a compartment therebetween is formed, thesaid compartmentbeing closed at both ends, an opening through the wallof the innermost tube-to provide communication between its interior andthe said compartment near one end of said compartment, a line ofdischarge openings in the wall of the intermediate tube, and a slot inthe outer tube registering with the said line of discharge openings topermit direct access or the heating fluid from the aforementionedcompartment to the chamber between the exterior of v the outer tube andthe inside of said shell.

3. In a continuous web drier, a series of drier rolls, each rollincluding a hollow cylindrical shell for supporting the 'web and aheating fluid distributor shaft upon which said shell is mounted fortree'rotation, said shaft comprising three concentric tubes, theinnermost tube being confor supporting theweb and a heating fluid dis--nected to a source of heating fluid at one end and closed at the otherend, the intermediate tube being larger than the innermost tube wherebya compartment therebetween is formed, the

said compartment being closed at both ends. an

opening through the wall of the innermost tube to provide communicationbetween its interior and the said compartment near one end of saidcompartment, a line of discharge openings in the wall 01 theintermediate tube, and a slot in the outer tube registering with thesaid line of discharge' openings to permit direct access ofthe,

heating fluid from the aforementioned compartment to the chamber betweenthe exterior of the outer tube and the inside of said shell, theadjacent upper and lower rolls in the operating sequence being. arrangedto have the heating

